Mini excavator
2011]] A compact or mini excavator is a tracked or wheeled vehicle with an approximate operating weight from 0.7 to 7.5 tonnes. It generally includes a standard backfill blade and features independent boom swing. Hydraulic Excavators are somewhat different from other construction equipment in that all movement and functions of the machine are accomplished through the transfer of hydraulic fluid. The compact excavator's work group and blade are activated by hydraulic fluid acting upon hydraulic cylinders. The excavator's slew (rotation) and travel functions are also activated by hydraulic fluid powering hydraulic motors. Structure Most compact hydraulic excavators have three distinct assemblies: house, undercarriage and workgroup. House The house structure contains the operator's compartment, engine compartment, hydraulic pump and distribution components. The house structure is attached to the top of the undercarriage via a swing bearing. The house, along with the workgroup, is able to rotate or slew upon the undercarriage without limit due to a hydraulic distribution valve which supplies oil to the undercarriage components. Slew Slewing refers to rotating the excavator's house assembly. Unlike a conventional backhoe, the operator can slew the entire house and workgroup upon the undercarriage for spoil placement. Undercarriage The undercarriage consists of rubber or steel tracks, drive sprockets, rollers, idlers and associated components/structures. The undercarriage supports the house structure and the workgroup. Variations Special versions have been developed by several manufacturer. * Variable track width. The trackframes are mounted on a slider arrangement and can be pulled in for transit ant to fit through doorways and then extended to work giving the machine more stability. * Tilting undercarriage - the track frame and base is fitted with a hinge between it and the slew ring and a short tilt ram. The upper structure the can then be levelled automatically or manually to allow the boom to operate vertically for cutting trenches across sloped with less over dig and with the machine being more stable Workgroup The workgroup (upper structure) of a compact hydraulic excavator consists of the boom, dipper or arm, and attachment (e.g. auger, bucket or breaker). It is connected to the front of the excavator's house structure via a swing frame that allows the workgroup to be hydraulically pivoted left or right to achieve offset digging for trenching parallel with the tracks. Independent Boom Swing The primary purpose of boom swing is for offset digging around obstacles or along foundations, walls or forms. A secondary use is cycling in areas too narrow for cab rotation. Independent boom swing is one of the major advantages of a compact excavator over other excavation equipment. Some machines are fitted with an Offset or variable geometry boom that allows digging close to and parallel to a wall with out the upper structure being rotated. On larger machines a trench can be dug parallel to the tracks but outside the width of the machine. Backfill blade The backfill blade is used for grading, levelling, backfilling, trenching, and general dozer work. The blade can be used to increase dump height and digging depth depending on its position in relation to the excavator's workgroup, this makes it very versatile. Some machines have blades with 'folding' wings or removable sections to reduce transit width. (especially on variable track width models). Attachments In recent years, hydraulic excavator capabilities have expanded far beyond excavation tasks. With the advent of hydraulic powered attachments such as a tiltrotator, breaker, a grapple or an auger, the excavator is frequently used in many applications other than excavation and with the tiltrotator attachment, actually serves as an effective tool carrier. Many excavators feature quick coupler (quick-attach) mounting systems for simplified attachment mounting, dramatically increasing the machine's utilization on the jobsite, with the provision of extra services with variable flows and integrated controls. Zero-tail Swing There are two distinct classes of compact excavators, conventional tail swing - units that have a rear counterweight that will extend beyond the tracks when the house rotates, and zero-tail swing - units with a house whose diameter stays within the width of the tracks through full rotation. Zero-tail swing units allow the operator to focus on digging and not watching where he or she is swinging. Micro excavators Some Japanese manufactures build machines as small as 700kg that can be moved in a small van or pick up and fit through the smallest standard doorways to work inside buildings. On the smallest ones the operator stands on a platform Notable manufacturers * Bobcat Company (Owned by Doosan Infracore - formerly Daewoo Heavy Industries & Machinery) * Caterpillar Inc. * Fermec * JCB * John Deere - in USA * Komatsu * Kubota * Pel-Job (Now branded Volvo) * Takeuchi Manufacturing * Terex - (was Fermec) * Volvo Construction Equipment * Wacker Neuson Group * Yanmar See also * Construction Plant Manufactures References / sources based on a wikipedia stub External links * Compact Excavator Specifications and Comparisons Category:Construction equipment category:Excavators Category:Tracked_vehicles Category:Mini Excavators Category:Machine types